When we perceive our environment, we rapidly integrate large amounts of incoming stimulus information into categories that help to guide our understanding of the world. Some stimuli are more relevant for our well-being and survival than others, for example stimuli that signal a threat or an opportunity for growth and expansion. In this review we examine the special role of such ‘‘emotional'' stimuli in perception and categorisation. To this end, we first discuss some fundamental aspects of perception, with an emphasis on the cognitive process of categorisation. We then tackle the questions: ‘‘What is an emotional stimulus?'' and ‘‘What is an emotion category?'' Afterwards, we illustrate, with a review of key findings from the empirical literature, (i) how stimuli are categorised as emotional, and (ii) how the perceptual processing of emotional stimuli is prioritised to allow for a rapid preparation of adaptive responses. To conclude, we discuss how research on the perception of emotional stimuli can contribute to current debates in psychology, namely (i) about the role of bottom-up vs. top-down factors in emotional processing and experience, and (ii) about the nature of the relationship between cognition and emotion.